JPH10255846A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having high capacity stability and improved effective energy density by preventing the capacitive degradation of electrodes, by using a negative electrode capable of storing- releasing Li, a positive electrode containing Li and a nonaqueous electrolyte containing LiClO4 as well as LiN(CF3 SO2 )2 as electrolyte. SOLUTION: A negative electrode 4 using a substance capable of storing- releasing Li, for example, Li metal, a carbonaceous material or the like as an active material and a positive electrode 1 using a laminated composite oxide or the like containing Li, Ni, B and Mn as an active material, are wound by sandwiching a separator 3, and the obtained electrode group is housed in a negative electrode can 7, and a nonaqueous electrolyte containing electrolyte is filled to provide a nonaqueous electrolyte secondary battery. The electrolyte contains LiN(CF3 SO2 )2 and LiClO4 as a sub-component in the molar ratio of (1:1) to (19:1), with the total concentration of 0.5 to 2 mole/l. Thus, the reaction of the electrolyte with a current collecting body or the like and water is restrained, and the degradation of the positive electrode containing Ni as an active material can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery in which imide salt LiN (CF ₃ SO ₂ ) ₂ can be used as an electrolyte of the non-aqueous electrolyte.

[0002]

2. Description of the Related Art Conventionally, in a lithium secondary battery using a metal oxide-based compound having a layered structure as a positive electrode and a compound capable of inserting and extracting lithium ions as a negative electrode, LiCLO ₄ , LiBF ₄ , Li
AsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiAlC
lithium salt l ₄ etc. are used.

[0003] With respect to metal oxide compounds for the positive electrode, LiCoO ₂ and LiNiO ₂ have attracted attention because they have an electromotive force of 4 V and a large theoretical energy density.

[0004]

However, in the case of the combination with the above-mentioned electrolyte and cathode material, there are the following problems.

[0005] First, the electrolyte of the above system represented by LiPF ₆ has a problem that, when water is contained in the electrolyte, it reacts with water to generate hydrogen fluoride.
That is, hydrogen fluoride is a very strong acid, and functions to impair the function not only of the battery can but also of the current collector and the active material. Therefore, it is indispensable to remove water from the electrolyte, but strict control is required, and it is difficult to completely remove a substance that is reactive with the active material such as moisture in the battery.

Next, regarding the lithium oxide of the positive electrode,
In the case where the lithium oxide of the positive electrode is a composite oxide having a layered structure containing Ni, since the reactivity with water and the like is large and the stability is poor, a non-aqueous electrolyte secondary battery using the same as the positive electrode is used. , The battery capacity is greatly degraded. Further, the decomposition potential of the positive electrode is at a low potential near 4.2 V,
This also has problems to be solved, such as increasing the deterioration of the capacity.

Therefore, in order to eliminate the capacity deterioration of the battery, the imide salt Li which does not need to be strictly controlled as described above is required.
By using N (CF ₃ SO ₂ ) ₂ for the electrolyte of the non-aqueous electrolyte, it is conceivable to improve the stability of the positive electrode active material and stabilize the capacity.

However, practically, there is no example in which this imide salt is used for a non-aqueous electrolyte secondary battery. The reason is that when an imide salt is used for the electrolyte of the non-aqueous electrolyte, a reaction with the aluminum foil constituting the positive electrode current collector is inevitable. In experiments conducted by the present inventors, in the case of using the imide salt LiN (CF ₃ SO ₂ ) ₂ alone,
It was confirmed that the corrosion of aluminium caused the deterioration of the battery capacity in the discharge test, but that it was hardly affected by moisture.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-aqueous electrolyte secondary battery in which an imide salt which has not been practically used until now can be used as an electrolyte of the non-aqueous electrolyte. In particular, the presence and generation of free acid due to moisture, which is a cause of capacity deterioration, in a positive electrode containing Ni as an active material is suppressed, and the capacity and stability of the nonaqueous electrolyte secondary battery are improved. The purpose is to increase the density.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the imide salt LiN (CF ₃ SO ₂ ) ₂ , which is difficult to use by itself, has been replaced with perchlorine It has been found that in an electrolyte in which lithium oxide LiClO ₄ coexists, it can be used without reaction of aluminum. That is, capacity deterioration of a battery using a positive electrode active material composed of a composite oxide having a layered structure containing Ni is suppressed by an electrolyte in which imide salt LiN (CF ₃ SO ₂ ) ₂ and lithium perchlorate LiClO ₄ coexist. You.

Specifically, the non-aqueous electrolyte secondary battery of the present invention according to the first aspect of the present invention provides a non-aqueous electrolyte secondary battery comprising: a negative electrode made of a substance capable of inserting and extracting lithium; a positive electrode containing nickel; A non-aqueous electrolyte containing (CF ₃ SO ₂ ) ₂ and LiClO ₄ is provided. In other words, LiN (CF
Using an organic electrolyte containing ₃ SO ₂ ) ₂ and LiClO ₄ ,
A positive electrode active material containing at least Ni is used.

Here, particularly, this electrolytic solution becomes more effective by replacing a part of Ni with cobalt, boron, and manganese and combining it with a stabilized cathode active material.

More specifically, the active material of the positive electrode containing nickel is represented by the general formula Li (Nix, By, Mnz) O ₂ [0.65 ≦ x ≦ 0.94,0 .01 ≦ y ≦ 0.0
5, 0.05 ≦ z ≦ 0.30], or as defined in claim 3, the general formula Li (Nix, Coy, Mnz) O ₂ [0. 45 ≦ x ≦ 0.80, 0.10 ≦ y ≦ 0.5
0, 0.10 ≦ z ≦ 0.45].

For such a positive electrode active material, a composition having an effect of suppressing a change in the layer structure at a potential of about 4.2 V by substituting the-part of Ni is used in combination with the electrolytic solution. Thereby, the capacity of the nonaqueous electrolyte secondary battery can be stabilized, and the effective energy density can be improved.

Further, as the battery type, lithium or a lithium alloy may be used for the negative electrode active material of the counter electrode, or a carbonaceous material capable of inserting and extracting lithium may be used. It may be something.

Further, the total concentration of the electrolyte is 0.5 mol / L to 2 mol / L, and LiN (CF ₃ SO ₂ ) ₂ and Li as a sub-component are contained in the electrolyte.
The molar ratio with ClO ₄ is preferably in the range of 1: 1 to 19: 1.

As described above, the electrolyte salt used in the non-aqueous electrolyte secondary battery includes LiPF ₆ , LiBF ₄ , and LBF.
iClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ S
O ₂ ) ₂ etc. When the free acid due to moisture is present in the organic electrolyte, the positive electrode active material made of a composite oxide having a layered structure containing Ni causes a large capacity deterioration even at a low concentration of about 10 ppm. In such a relationship, the imide salt LiN (CF ₃ SO ₂ ) ₂
When an electrolytic solution is used as an electrolyte in which lithium is combined with lithium perchlorate LiClO ₄ , the influence on the positive electrode active material is small, and the capacity of the battery is hardly deteriorated.

In this case, LiN (CF ₃ SO ₂ ) ₂ and L
As for the concentration of iClO ₄ , the total concentration is preferably from 0.1 mol / l to 2 mol / l. The reason is that in the range of 0.1 mol / liter or less and the range exceeding 2 mol / liter, the discharge capacity is already small from the beginning of the discharge test (see Table 7). More preferably, it is in the range of 0.8 mol / l to 1.6 mol / l (see Table 7).

Further, LiN (CF ₃ SO ₂ ) ₂ and LiC
The mixing ratio of 10 ₄ is preferably in the range of 1: 1 to 19: 1 in molar ratio. The reason is that when this molar ratio is smaller than 1: 1, the characteristics become close to those of lithium perchlorate, and the cycle characteristics in charge and discharge, that is, the discharge capacity after repeating the charge and discharge test a certain number of times, and further thereafter When the ratio (%) to the discharge capacity after repeated a predetermined number of times becomes worse (see Tables 5 and 6 where the molar ratio is 1: 2), and when the molar ratio exceeds 19: 1, This is because the salt becomes close to the case of the salt alone and a reaction with the aluminum foil of the positive electrode current collector occurs, so that a desired capacity cannot be obtained from the time of the initial charge / discharge test, and the cycle characteristics also deteriorate. Imide salt Li
N (CF ₃ SO ₂ ) ₂ and lithium perchlorate LiClO ₄
Is more preferably in the range of 5: 1 to 15: 1, which is not biased to any of the above ranges.

When the above-mentioned electrolyte is used, a high conductivity can be obtained, and the influence of free acid which corrodes the battery can and the current collector can be suppressed.

As the organic solvent, a mixed solution of a high dielectric constant solvent such as propylene carbonate and ethylene carbonate and a low viscosity solvent such as dimethylene carbonate and diethylene carbonate in an equal volume ratio is preferable.

[0022]

Embodiments of the present invention will be described below.

FIG. 1 shows the overall structure of a prototype lithium ion secondary battery, and FIG. 2 shows the structure of its electrodes. As shown in the figure, a lithium ion battery has a positive electrode 1 in which a layered composite oxide containing Ni as a positive electrode active material is applied to a positive electrode current collector 2 made of aluminum foil, and a separator 3 disposed on the front and back thereof. A negative electrode 4 having a copper foil as a negative electrode current collector 5 is disposed on one side thereof, and the negative electrode 4 is wound around the negative electrode 4 to form an electrode group 6, which is disposed in a negative electrode can 7.

The electrolytic solution is an imide salt LiN (CF ₃ S
The organic electrolyte contains O ₂ ) ₂ and secondary components such as lithium perchlorate LiClO ₄ .

Of Examples 1 to 4 described below, Examples 1 and 2 are for the case where the negative electrode is made of a carbonaceous material, and Examples 3 and 4 are different in type from those described above. Is the case of metallic lithium.

(1) Example 1 First, the positive electrode 1 was made of lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), and cobalt oxide (C
o ₂ O ₃ ) and manganese dioxide (MnO ₂ ) with Li: N
In i: Co: Mn, the mixture was weighed so as to have a predetermined molar ratio shown in Table 1 and sufficiently mixed using a mortar. The mixture was heated and calcined at a temperature of 650 ° C. for 24 hours in an oxygen stream, and then cooled. The powder was pulverized to a particle size of 20 μm or less to obtain a positive electrode active material.

91 parts by weight of this positive electrode active material, 6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride as a binder were mixed, and 100 parts by weight of N-methylpyrrolidone as a solvent were further added. Into a slurry. This slurry is uniformly applied to both sides of a current collector made of an aluminum foil having a thickness of 20 μm, and dried. After drying, compression molding with a roller press machine,
A belt-shaped positive electrode having a thickness of 200 μm was produced.

Next, the negative electrode was prepared by mixing ground pitch coke with 9 pieces.
0 parts by weight and 10 parts by weight of polyvinylidene fluoride as a binder are mixed, and 100 parts by weight of N-methylpyrrolidone as a solvent is added to form a slurry. This slurry is uniformly applied to both surfaces of a 10 μm thick copper foil of the current collector 5 and dried. After drying, compression molding was performed using a roller press machine to produce a 200 μm-thick strip-shaped negative electrode. Leads were low-welded to each current collector so as to be alternately arranged vertically.

Next, the positive electrode 1 and the negative electrode 4
A single spirally wound electrode 6 is formed by using one separator 3 made of a microporous polypropylene film having a thickness of 0 μm and laminating and winding each other. This was inserted into the battery outer can 7.

Then, an explosion-proof valve was welded to the tip of the positive electrode lead by passing an insulating plate from the tip of the lead. The negative electrode lead side was welded to the bottom of the battery outer can.

The electrolyte of the present invention, namely, LiN (CF ₃ S
An electrolyte containing O ₂ ) ₂ and containing LiClO ₄ is dissolved in the electrolyte, and LiN (CF ₃ SO ₂ ) ₂ and LiClO ₄
Were adjusted to a molar ratio of 15: 1 and an electrolyte concentration of 1.6 Mol / l. For comparison, an electrolytic solution using LiPF ₆ as the electrolyte was similarly prepared.

The above-prepared electrolytic solution was injected to impregnate the wound electrode 6, an explosion-proof valve and a closing lid were overlapped, their outer peripheries were brought into close contact with a gasket, and the battery was sealed with a battery outer can.

The initial capacity and the capacity after 60 cycles of the battery thus manufactured were measured under the following conditions. Table 1 shows the results of the charge / discharge test.

[0034]

[Table 1]

Table 1 shows the case where the negative electrode is made of a carbonaceous material.
The electrolyte had a molar ratio of LiN (CF ₃ SO ₂ ) ₂ to LiClO ₄ of 15: 1 and an electrolyte concentration of 1.6 Mol / l. Outer products and prototype examples 3 and 4 are within the scope of the present invention. 1st, 60
th is the battery capacity (mAh) when the charge / discharge cycle in the charge / discharge test is the first and 60th, respectively.
Is shown. When comparing the charge and discharge capacities of Prototype Examples 3 and 4 according to the present invention with a comparative example in which the right electrolyte was LiPF ₆ , both the initial battery capacity and the cycle characteristics were considerably improved, and the characteristics were improved. It can be seen that there is a considerable difference.

(2) Example 2 First, the positive electrode 1 was made of lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), and boric acid (H ₃ BO).
₃ ) and manganese dioxide (MnO ₂ ) by Li: Ni: B:
In Mn, the mixture was weighed so as to have a predetermined molar ratio shown in Table 2 and sufficiently mixed using a mortar. The mixture was heated and calcined at a temperature of 650 ° C. for 24 hours in an oxygen stream, and after cooling,
The powder was pulverized to a particle size of 20 μm or less to obtain a positive electrode active material. 91 parts by weight of this positive electrode active material and 6 parts of graphite as a conductive agent
3 parts by weight of polyvinylidene fluoride as parts by weight and binder
Parts by weight, and 100 parts by weight of N-methylpyrrolidone as a solvent is added to form a slurry. This slurry is uniformly applied to both sides of a current collector made of an aluminum foil having a thickness of 20 μm, and dried. After drying, compression molding was performed using a roller press machine to form a 200 μm-thick strip-shaped positive electrode.

Next, 90 parts by weight of the crushed pitch coke and polyvinylidene fluoride 10 as a binder are mixed at a ratio of 90 parts by weight, and 100 parts by weight of N-methylpyrrolidone as a solvent is added to the negative electrode 4 to form a slurry. . This slurry is uniformly applied to both sides of a current collector made of a copper foil having a thickness of 10 μm and dried. After drying, compression molding was performed using a roller press machine to produce a 200-μm-thick band-shaped negative electrode. Leads were resistance-welded to the respective current collectors so as to be alternately arranged vertically.

Next, a thickness of 20 μm was applied to the positive electrode and the negative electrode.
3 made of microporous polypropylene film
Is used, and these are laminated and wound to form a spirally wound spiral electrode 6. This was inserted into the battery outer can 7.

Then, an explosion-proof valve was welded to the tip of the positive electrode lead through an insulating plate from the tip of the lead. The negative electrode lead side was welded to the bottom of the battery outer can 7.

The electrolyte of the present invention, namely, LiN (CF ₃ S
An electrolyte containing O ₂ ) ₂ and containing LiClO ₄ is dissolved in the electrolyte, and LiN (CF ₃ SO ₂ ) ₂ and LiClO ₄
Were adjusted to a molar ratio of 15: 1 and an electrolyte concentration of 1.6 Mol / l.

The above-prepared electrolytic solution was injected to impregnate the wound electrode 6, the explosion-proof valve and the closing lid were overlapped, their outer circumferences were brought into close contact with a gasket, and the battery was sealed with a battery outer can 7. .

The initial capacity and the capacity after 60 cycles of the battery thus manufactured were measured under the following conditions. Table 2 shows the results of the charge / discharge test.

[0043]

[Table 2]

Table 2 is the same as Table 1 except for the composition of the positive electrode. That is, the negative electrode is made of a carbonaceous material as in Table 1, and the electrolyte is LiN
The molar ratio of (CF ₃ SO ₂ ) ₂ to LiClO ₄ is 15:
1. The electrolyte concentration is 1.6 Mol / l. Prototype examples 6, 7, and 10 are outside the scope of the present invention, and prototype examples 8 and 9 are within the scope of the present invention. The first charge / discharge cycle,
When the charge and discharge capacity (mAh) of Prototype Examples 8 and 9 according to the present invention for the 60th time was compared with the comparative example (when the electrolytic solution was LiPF ₆ ) shown on the right side of Table 1 above, the initial battery was also found. It can be seen that the capacity and cycle characteristics have been significantly improved.

(3) Example 3 First, the positive electrode was made of lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), and cobalt oxide (Co).
₂ O ₃ ) and manganese dioxide (MnO ₂ ) with Li: Ni:
In Co: Mn, the mixture was weighed so as to have a predetermined molar ratio shown in Table 3 and sufficiently mixed using a mortar. Then, the mixture was heated and calcined at a temperature of 650 ° C. for 24 hours in an oxygen stream, cooled, and cooled. The powder was pulverized to a diameter of 20 μm or less to obtain a positive electrode active material.
75 parts by weight of this positive electrode active material, 12.5 parts by weight of acetylene black as a conductive agent, and 1 part of Teflon as a binder
2.5 parts by weight were mixed to produce homogeneous pellets. The pellet was adhered to a titanium mesh current collector to form a positive electrode.

Next, metallic lithium (or lithium-
Aluminum alloy) ribbon is punched in a predetermined area,
A negative electrode was made.

The positive and negative electrodes were welded to the bottom of the coin-shaped cell and opposed to each other.

The electrolyte of the present invention, namely, LiN (CF ₃ S
An electrolyte containing O ₂ ) ₂ and containing LiClO ₄ is dissolved in the electrolyte, and LiN (CF ₃ SO ₂ ) ₂ and LiClO ₄
Were adjusted to a molar ratio of 15: 1 and an electrolyte concentration of 1.6 Mol / l. For comparison, an electrolytic solution using LiPF ₆ as the electrolyte was similarly prepared.

Next, between the positive electrode and the negative electrode, 20 μm
m, a separator made of a microporous polypropylene film was sandwiched, the above-prepared electrolytic solution was injected, and their outer peripheries were brought into close contact with a gasket and sealed by caulking.

Using the coin-shaped cell thus produced, the initial capacity and the capacity after 60 cycles were measured under the following conditions. Table 3 shows the results of the charge / discharge test.

[0051]

[Table 3]

Table 3 shows that the negative electrode was metallic lithium and LiN
The molar ratio of (CF ₃ SO ₂ ) ₂ to LiClO ₄ is 15:
1. The electrolyte concentration is 1.6 Mol / l. Prototype example 1
1, 12, and 15 are out of the scope of the present invention,
14 is within the scope of the present invention. When the charge and discharge cycles are the first and the 60th, the charge and discharge capacity (mAh) of the prototypes 13 and 14 according to the present invention is compared with the comparative example on the right side (when the electrolyte is LiPF ₆ ). Significant improvements in initial battery capacity and cycle characteristics are seen.

(4) Example 4 First, the positive electrode was made of lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), and boric acid (H ₃ B).
O ₃ ) and manganese dioxide (MnO ₂ ) with Li: Ni:
B: Mn was weighed so as to have a predetermined molar ratio shown in Table 4 and thoroughly mixed using a mortar. The mixture was heated and calcined in an oxygen stream at a temperature of 650 ° C. for 24 hours, and cooled. Thereafter, the powder was pulverized to a particle size of 20 μm or less to obtain a positive electrode active material.
75 parts by weight of this positive electrode active material, 12.5 parts by weight of acetylene black as a conductive agent, and 1 part of Teflon as a binder
2.5 parts by weight were mixed to produce homogeneous pellets. The pellet was adhered to a titanium mesh current collector to form a positive electrode.

Next, metallic lithium (or lithium-
Aluminum alloy) ribbon is punched in a predetermined area,
A negative electrode was made.

The positive and negative electrodes were welded to the bottom of the coin-shaped cell and opposed to each other.

The electrolyte of the present invention, namely, LiN (CF ₃ S
An electrolyte containing O ₂ ) ₂ and containing LiClO ₄ is dissolved in the electrolyte, and LiN (CF ₃ SO ₂ ) ₂ and LiClO ₄
Were adjusted to a molar ratio of 15: 1 and an electrolyte concentration of 1.6 Mol / l.

Next, regarding the positive electrode and the negative electrode, 20 μm
m, a separator made of a microporous polypropylene film was sandwiched, the above-prepared electrolytic solution was injected, and their outer peripheries were brought into close contact with a gasket and sealed by caulking.

Using the coin-shaped cell thus produced, the initial capacity and the capacity after 60 cycles were measured under the following conditions. Table 4 shows the results of the charge / discharge test.

[0059]

[Table 4]

Table 4 is the same as Table 3 except for the composition of the positive electrode. That is, the case where the negative electrode is metallic lithium, and the electrolyte is LiN (CF ₃ SO ₂ ) ₂ and L
iClO ₄ molar ratio 15: 1, electrolyte concentration 1.6 M
ol / l. Prototype examples 16, 17, and 20 are outside the scope of the present invention, and prototype examples 18 and 19 are within the scope of the present invention. For the first and 60th charge / discharge cycles, the charge / discharge capacities (mAh) of the prototypes 18 and 19 of the present invention.
Is compared with the comparative example on the right side of Table 3 (when the electrolytic solution is LiPF ₆ ), it can be seen that the initial battery capacity and the cycle characteristics are also considerably improved.

(5) Examples of Other Prototypes Tables 5 and 6 show the above Tables 3 and 4 using metallic lithium for the negative electrode.
In the case of Table 4, the imide salt LiN (CF
These data are obtained when the molar ratio of ₃ SO ₂ ) ₂ to lithium perchlorate LiClO ₄ is changed to 1: 2.

[0062]

[Table 5]

[0063]

[Table 6]

As can be seen by comparing the data in Tables 5 and 6 with the trial number 14 in Table 3 and the trial number 19 in Table 4, as shown in Tables 5 and 6, the imide salt and perchloric acid When the molar ratio of lithium was reduced to 1: 2, the result of the charge / discharge test showed that the charge / discharge capacity (mAh) at the 60th time was considerably smaller than that in the case where the molar ratio was 15: 1, and the cycle characteristics deteriorated. It becomes remarkable and becomes almost the same as the conventional comparative example. This is because the imide salt LiN (C
It is considered that when the molar ratio of F ₃ SO ₂ ) ₂ to lithium perchlorate LiClO ₄ is smaller than 1: 1, the characteristics are close to those of lithium perchlorate. Therefore, the LiN
The molar ratio of (CF ₃ SO ₂ ) ₂ to LiClO ₄ is 1: 1
It is better to stop by. Although not shown as an experimental example, the molar ratio of the imide salt to lithium perchlorate was 19:
If it exceeds 1, the case becomes close to the case of the imide salt alone, and corrosion of the aluminum foil of the positive electrode current collector occurs, so that a desired capacity cannot be obtained from the initial charge / discharge test, and the cyclability also deteriorates. Therefore, LiN (CF ₃ SO ₂ ) ₂ and LiC
The mixing ratio of 10 ₄ is preferably in the range of 1: 1 to 19: 1 in terms of molar ratio, and more preferably in the range of 5: 1 to 15: 1 which is not biased to any of the above ranges.

Table 7 shows that the imide salt LiN (CF ₃
It shows the initial discharge capacity (%) when the value of the total concentration (Mol / l) of SO ₂ ) ₂ and lithium perchlorate LiClO ₄ was changed.

[0066]

[Table 7]

From Table 7, it can be seen that LiN (CF ₃ SO ₂ ) ₂ and L
Regarding the concentration of iClO ₄ , the total concentration was 0.1 (M
(mol / l) to 2 (Mol / l). 0.1 (Mol / l) or less and 2 (Mol / l)
This is because in the range exceeding l), the discharge capacity is already less than 80% from the beginning of the discharge test. From Table 7, it can be seen that a more preferable concentration is in the range of 0.8 (Mol / l) to 1.6 (Mol / l).

[0068]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) The non-aqueous electrolyte secondary battery according to the first aspect is characterized in that a negative electrode made of a substance capable of inserting and extracting lithium, a positive electrode containing nickel, and at least LiN (CF ₃ SO _{3) 2} ) LiClO ₄ containing ₂
And a non-aqueous electrolytic solution containing: The imide salt LiN (CF ₃ SO ₂ ) _2, which is difficult to use by itself, can be used by suppressing the reaction of the current collector with aluminum by coexistence with lithium perchlorate LiClO _4. A positive electrode containing Ni as a substance can suppress the presence and generation of free acid due to moisture, which is a cause of capacity deterioration, and can suppress a decrease in battery capacity. Therefore,
By using this electrolyte in a secondary battery that uses a positive electrode active material composed of a composite oxide having a layered structure containing Ni, the capacity is stabilized and the effective energy density is improved. Thus, battery characteristics with a high energy density different from the above can be obtained.

(2) In particular, the function of this electrolytic solution is to partially convert Ni to cobalt.
By combining with a positive electrode active material having an increased decomposition potential by substituting with boron / manganese, the effect becomes more effective, and the capacity of the nonaqueous electrolyte secondary battery can be stabilized, and the effective energy density can be improved.

(3) Further, as for this function and effect, as described in claim 4, the battery type is one using lithium or a lithium alloy as the negative electrode active material of the counter electrode, or capable of inserting and extracting lithium. And those using a suitable carbonaceous material.

(4) Further, the above-mentioned effect is obtained when the total concentration of the electrolyte is 0.5 to 2 mol / liter, and LiN (CF ₃ SO ₂ ) ₂ and the subcomponent By adjusting the molar ratio of LiClO ₄ to be in the range of 1: 1 to 19: 1, the result becomes particularly remarkable, and a practical nonaqueous electrolyte secondary battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, which is partially developed.

FIG. 2 is a perspective view showing an electrode structure of the non-aqueous electrolyte secondary battery of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode 2 positive electrode current collector 3 separator 4 negative electrode 5 negative electrode current collector 6 electrode group 7 negative electrode can

Claims (5)

[Claims] An anode (4) made of a substance capable of inserting and extracting lithium, and an anode (1) containing nickel.
And a non-aqueous electrolyte secondary battery containing at least LiN (CF ₃ SO ₂ ) ₂ in the electrolyte and containing LiClO ₄ . 2. The active material of the positive electrode (1) is represented by a general formula Li (Nix, By, Mnz) O ₂ [0.65 ≦ x ≦ 0.94, 0.01 ≦ y ≦ 0.0
5. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is composed of a composite oxide having a layered structure satisfying the condition: 5, 0.05 ≦ z ≦ 0.30]. 3. The active material of the positive electrode (1) is represented by a general formula Li (Nix, Coy, Mnz) O ₂ [0.45 ≦ x ≦ 0.80, 0.10 ≦ y ≦ 0.5
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is composed of a composite oxide having a layered structure in which 0, 0.10 ≦ z ≦ 0.45]. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein lithium, a lithium alloy, or a carbonaceous material capable of inserting and extracting lithium is used as the negative electrode active material. 5. The method according to claim 1, wherein the total concentration of the electrolyte is 0.5 mol / l to 2 mol / l and the concentration of LiN (CF ₃ SO
_2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the molar ratio of ₂ to LiClO _{4 as} a subcomponent is 1: 1 to 19: 1.